12Cr/30Cr2Ni4MoV异种转子钢焊接接头微区冲击韧性研究

A welded joint of dissimilar rotor steels (12Cr/30Cr2Ni4MoV) with a transition layer was fabricated using the combined welding technology of narrow - gap tungsten inert gas (NG - TIG) and narrow - gap submerged arc welding (NG - SAW). The shear strength of the micro - regions of the joint was obtained by micro - shear tests, and the ductile - brittle transition temperature FATT_(50) of the micro - regions was obtained by the partition testing method. The influence of the microstructure on the micro - region hardness, strength and toughness was studied. The research results show that the distribution characteristics of the hardness and shear strength of the welded joint are basically the same, the mechanical properties in the heat affected zone are distributed in a gradient, and the mechanical properties on both sides of the fusion line interface are mismatched; there is a local weakened area in the transition layer, with a microhardness of 227 HV, which is the weakest area of the entire welded joint; from the base metal 12Cr to 30Cr2Ni4MoV, the ductile - brittle transition temperature FATT_(50) of the joint micro - regions gradually decreases; at 20 °C, the impact toughness of the base metal 30Cr2Ni4MoV and its heat affected zone is excellent, cracks initiate at the matrix/second phase interface, and ductile fracture occurs through micropore aggregation, and quasi - cleavage fracture occurs in the remaining micro - regions, and the impact toughness of the weld is the worst.

采用窄间隙钨极氩弧焊(Narrow-gap tungsten inert gas,NG-TIG)和窄间隙埋弧焊(Narrow-gap submerged arc welding,NG-SAW)组合焊接技术制造了带有过渡层的异种转子钢焊接接头(12Cr/30Cr2Ni4MoV)。采用微剪切试验获得了接头微区的剪切强度,通过分区测试法获得了微区韧脆转变温度FATT_(50),研究了显微组织对微区硬度、强度和韧性的影响。研究结果表明,焊接接头的硬度和剪切强度分布特征基本一致,热影响区力学性能梯度分布,熔合线界面两侧力学性能不匹配;过渡层存在局部弱化区,显微硬度为227 HV,为整个焊接接头最为薄弱的区域;由母材12Cr过渡至30Cr2Ni4MoV,接头微区脆韧转变温度FATT_(50)逐渐降低;20 ℃下,母材30Cr2Ni4MoV及其热影响区冲击韧性优异,裂纹萌生于基体/第二相界面,通过微孔聚集发生韧性断裂,其余微区均发生准解理断裂,焊缝冲击韧性最差。